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DP159 - Cannot lock to 1 lane 5.4Gbps DisplayPort data

Kawai
Guru 19785 points


Hello Team,

We are having trouble that DP159EVM would not lock to 1 lane 5.4Gbps DisplayPort signal. Could you please help us acquire lock to the input signal ?
- Customer signal is not a video signal so we are not connecting SINK device.
- TMDS output is terminated with 50 Ohm to 3.3V.

[Q1]
Do you have any idea why DP159 would not lock to the input signal ?
Input signal data rate were 5.4Gbps -5ppm.

[Q2]
I believe DP159 retimer function would operate even if you don't have HPD_sink signal as long as you disable "HPD auto power down" function. Am I correct ?

[Q3]
We would like to evaluate the operation in our lab using DP159EVM, however we do not have DisplayPort signal generator. I believe you could use PRBS-7 signal generator instead of DP signal. Is there anything what we must take care ?

Best Regards,

Kawai

  • 0
    TI__Guru 60870 points
    Hi Kawai,

    A1. Please note that the DP159 is a Dual Mode DP to HDMI retimer / redriver and level shifter. It is not a protocol conversion device. The DP159 is expecting AC coupled TMDS inputs, not standard DP inputs.

    A2. No, HPD SNK must be high for for DP159 to enable its outputs. The HPD auto power down function just enables / disables the low power mode when HPD SNK is low.

    A3. You can use a PRBS 7 generator, but for 6G operation, the 1/40th clock ratio bit will need to be set over DDC or forced on using i2C register access.

    Regards,
    JMMN
  • 0 in reply to JMMN
    Guru 19785 points

    Hello JMMN-san,

    Thank you for your reply.

    1) Yes, I am understanding DP159 is not a protocol conversion device. Customer DP signal is a system closed interface. They are expecting to improve jitter using the CDR. We were able to have output in redriver mode, however not output in retimer mode. Do you have any idea how to get the output ?

    2) I understand. I believe HPD_Snoop circuit would work. Customer is using this.

    3) I could not fully understand your answer. Do you mean I would not have problem as long as I control DP159 through Eyescan Tool ?

    Best Regards,

    Kawai

  • 0 in reply to Kawai
    Guru 19785 points
    JMMN-san,

    In addition to my above post, could you please advise me how to acquire lock to input 5.4Gbps PRBS-7 signal and output retimed data ?

    Please tell us the register settings if required. I am planning to evaluate with the EVM tomorrow morning.

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Guru 60870 points

    Hi Kawai,

    1) It doesn't matter if this is a closed system, the DP159 will not be able to retime the input data unless it is TMDS.  That is likely why the system is only working in redriver mode.  Can you confirm that there is a clock provided on the clock inputs (Lane 3)?

    2.  HPD snoop will work, but the HPD_SNK must still be connected to the DP159.

    3. The DP159 can retime any data, but it must have a clock to do so.  If the clock is set to 1/40th rate, the DP159 must be aware of it through the DDC or a direct register access (setting bits 1 and 0 in Register 0x0Bh).

    Regards,

    JMMN